SEARCH for Diabetes in Youth (SEARCH) is an on-going, multi-center study containing the largest and most ethnically diverse population of youth with diabetes ever studied in the US. In response to RFA-DP10-001, Component B, the SEARCH Cohort Study will utilize this unique resource by continuing the study of selected SEARCH participants to address the following Aims: 1) assess the prevalence, incidence, and risk factors for selected markers of chronic microvascular (retinopathy, nephropathy, and autonomic neuropathy) and macrovascular complications (hypertension, arterial stiffness) of diabetes;2) assess the incidence and risk factors for acute complications of diabetes including serious hypoglycemia and diabetic ketoacidosis;3) conduct surveillance of mortality;and 4) determine the degree to which barriers of care, quality of care, and transition to adult care impact diabetes-related health outcomes including quality of life. Overlaid across these Aims, we will focus on the impact of race/ethnicity and other sociocultural factors, and biochemical dimensions of diabetes type, on diabetes-related health outcomes. The SEARCH Cohort Study will conduct an in-person research study visit on SEARCH participants incident in 2002 or later, with duration of diabetes >5 years and with baseline data completed (expected n=3699). During this study medical history, anthropometric, biochemical, physiologic, and survey data will be collected and analyzed. The Washington SEARCH site includes 5 Puget Sound counties (King, Kitsap, Pierce, Thurston, and Snohomish) surrounding Seattle and Tacoma. We have successfully registered over 3,700 participants, and we are the second largest SEARCH site in terms of total number of surveys and baseline visits completed. With a high response rate to follow-up visits, and the significant expertise of Washington investigators in diabetes and its complications, we are strongly positioned to meet the aims of this study. This study will exploit the size and ethnic diversity of the study population to identify differences in both processes of care and health outcomes by traditional, clinical diabetes type;by the major race/ethnic groups in the US;and by employing a novel approach to segregate traditional clinical diabetes types by pathophysiologic dimensions. Thus, the SEARCH cohort study has a high likelihood of making a significant impact on the clinical care of youth with diabetes from all the major ethnic groups in the US and on national public health policy.